这个问题似乎是在ADT的错误。人工手动操作的清洁通过Project - >干净，然后再出口的APK解决了这一问题。

When I run my app directly from Android Developer Tools (ADT), it works fine. However, when I export it to an APK file and install it, I get the following error:

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{my.app/my.app.MainActivity}: java.lang.ClassNotFoundException: Didn't find class "my.app.MainActivity" on path: DexPathList[[zip file "/data/app/my.app-2.apk"],nativeLibraryDirectories=[/data/app-lib/my.app-2, /vendor/lib, /system/lib]] at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2187) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2311) at android.app.ActivityThread.access$600(ActivityThread.java:149) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1293) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5214) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:525) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.ClassNotFoundException: Didn't find class "my.app.MainActivity" on path: DexPathList[[zip file "/data/app/my.app-2.apk"],nativeLibraryDirectories=[/data/app-lib/my.app-2, /vendor/lib, /system/lib]] at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:53) at java.lang.ClassLoader.loadClass(ClassLoader.java:501) at java.lang.ClassLoader.loadClass(ClassLoader.java:461) at android.app.Instrumentation.newActivity(Instrumentation.java:1061) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178) ... 11 more

The problem seemed to be a bug in ADT. Manually doing a clean via Project -> Clean and then re-exporting the APK fixed the problem.